Drone rotor cage

ABSTRACT

Disclosed is a drone rotor cage. The drone rotor cage may include a motor housing, a plurality of spars, and a plurality of ribs. The plurality of spars may extend from the motor housing. Each of the plurality of spars may have a spar height and a spar thickness. The spar height may be greater than the spar thickness. Each of the ribs may extend from a respective one of the plurality of spars. Each of the plurality of ribs may have a rib height and a rib thickness. The rib height may be greater than the rib thickness. The plurality of spars and the plurality of ribs may define a space sized to allow a rotor to spin freely when the rotor cage is attached to a drone.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/721,126, filed Sep. 29, 2017, which is related to and claims priorityto U.S. Provisional Application No. 62/421,928 filed on Nov. 14, 2016,each of which is hereby incorporated in its entirety.

TECHNICAL FIELD

Embodiments described generally herein relate to drones. Someembodiments relate to a drone rotor cage.

BACKGROUND

An unmanned aerial vehicle (UAV), commonly known as a drone, is anaircraft without a human pilot aboard. The size of drones may range fromsmall hobby scale suitable for close range operation proximate a user tolarge scale systems capable of hauling large payloads over many miles.Drones may be used to provide services, perform military operations, oras a hobby.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numeralsmay describe similar components in different views. Like numerals havingdifferent letter suffixes may represent different instances of similarcomponents. The drawings illustrate generally, by way of example, butnot by way of limitation, various embodiments discussed in the presentdocument. The drawings are not necessarily drawn to scale and somedimensions may be exaggerated for clarity.

FIGS. 1A and 1B illustrate an example schematic of a drone in accordancewith some embodiments.

FIGS. 2A and 2B illustrate an example rotor cage in accordance with someembodiments.

FIGS. 3A and 3B illustrate an example rib in accordance with someembodiments.

FIGS. 4A and 4B illustrate an example spar in accordance with someembodiments.

FIG. 5 illustrates a rib in accordance with some embodiments.

FIG. 6 illustrates an example schematic of a drone in accordance withsome embodiments.

FIG. 7 illustrates an example method in accordance with someembodiments.

DETAILED DESCRIPTION

Drone usage is becoming more and more common as prices for dronesdecrease and the capabilities of drones increase. For example, asdisclosed herein, drones may be programmed to launch, flying apredefined flightpath, illuminate one or more onboard light emittingdiodes (LED), and recover to a predetermined location. All of theseactivities may be accomplished without user intervention. With theincreased drone capabilities and decreased costs, drone usage may beimplemented in a variety of entertainment, safety, or emergencyscenarios.

In general, drones may include any number of rotors, with four beingcommon. Rotor controllers may be used to control the rotors. The rotorcontroller may control one or more rotors. Each rotor may also include amotor.

During flight, one or more of the rotors may fail. The failure may bedue to, among other things, motor failure, a rotor controller failure,or physical damage to a rotor blade. When one or more of the rotorsfail, the drone may become unstable or otherwise incapable ofmaintaining flight. For example, if two adjacent rotors on a quadcopterfail, one side of the quadcopter may begin to fall and cause thequadcopter to no longer be able to maintain a horizontal attitude orlevel flight.

In addition to rotor failure the spinning rotors may present a hazard.For instance, when the rotor blades are spinning at a high rate ofspeed, the rotor blades may be difficult to see. As a result, thespinning rotor blades may cause injury to operators or spectators.

As disclosed herein, a cage may be placed around each of the rotors. Thecage may serve multiple purposes. For example, the cages may protectpersons or property from the spinning rotor blades. In addition, thecages may be constructed such that during a rotor failure, the cages mayassist in keeping the drone in a substantially horizontal state so thatthe drone may land safely.

FIGS. 1A and 1B illustrate an example schematic of a drone 100 inaccordance with some embodiments. The drone 100 may include rotors 102A,102B, 102C, and 102D (collectively rotors 102) that may be attached toan airframe 104. Each of the rotors 102 may include a rotor blade 106A,106B, 106C, and 106D (collectively rotor blades 106) and a motor 108A,108B, 108C, and 108D (collectively motors 108). The rotors 102 may besurrounded by a cage 110A, 110B, 110C, and 110D (collectively cages 110)and attached to the airframe 104 by rotor arms 112A, 112B, 112C, and112D.

During operation, the rotor blades 106 may spin at a high speed andgenerate lift to propel the drone 100 through the air. Depending on thespeed of the rotor blades 106 and the attitude of the drone 100, thedrone 100 may climb or descend. For example, if the drone 100 is in alevel attitude, and the rotor blades 106 begin spinning at a fasterspeed, the drone 100 may climb. If the rotor blades begin spinning at aslower speed, the drone 100 may descend.

If the drone 100 is not in a level attitude, increases or decreases inrotor blade 106 speeds may cause the horizontal and vertical componentsof lift to increase or decrease. Thus, increasing or decreasing therotor blade 106 speed, may cause the drone to move horizontally as wellas climb or descend. As a result, should one or more of the rotors 102malfunction, the drone 100 may develop asymmetric lift or otherwiseresult in the drone 100 being in an unusual attitude. For example,should rotors 102C and 102D malfunction, one side of the drone 100 maydescend as indicated by arrow 114. Other combinations of rotor failuremay also cause asymmetric lift.

The descending of one side of the drone 100 may cause a loss of flightcontrol. For example, as one side of the drone 100 descends, the otherside of the drone 100 may be forced into a vertical position. Theresult, may be that the remaining functional rotors may not be in aposition to generate vertical lift and instead may generate horizontallift. The horizontal lift may further aggravate the unusual attitude andloss of flight control.

As disclosed herein, the cages 110 may provide an aerodynamic effectsuch that during a rotor malfunction, the cages 110 may assist inmaintaining a horizontal attitude. Thus, during a rotor malfunction, thecages 110 may assist in maintaining flight control to assist in landingthe drone 100. The aerodynamic effect may be created by the shape of thecages 110. In addition, the remaining functional rotors 106 may beadjusted to assist with a controlled landing during a rotor malfunctionas disclosed herein.

While FIGS. 1A and 1B show a rotor cage for each rotor, embodiments mayinclude a rotor cage surrounding more than one rotor. For example, asingle rotor cage may surround two or more sets of rotor blades. Thus,the drone 100 may have two rotor cages sounding the rotor blades 106.

FIGS. 2A and 2B illustrate a cage 200 (such as one of the cages 110) inaccordance with some embodiments. As shown in FIGS. 2A and 2B, the cage200 may include a rotor motor housing 202 and a rotor arm connector 204.The rotor arm connector 204 and the rotor motor housing 202 may allowthe cage 200 to connect to the drone 100 at multiple locations.

The cage 200 may also include ribs 206 and spars 208. As shown in FIGS.3A and 3B the ribs 206 may have a height, H, that is greater than athickness, T. FIGS. 4A and 4B show that the spars 208 may have a height,H, that is greater than a thickness, T. The thickness of the spars 208and the ribs 206 may be the same or may be different. The height of thespars 208 and the height of the ribs 206 may be the same or may bedifferent. The height of the spars 208 and the height of the ribs 206may be twice the thickness of the ribs 206 and the spars 208.

By having the height be greater than the thickness, when the drone 100is in an unusual attitude, possibly caused by a rotor failure, a surfacearea of the ribs 206 and the spars 208 facing in a downward directionmay increase. The increased surface area may cause an increase in dragexperienced by drone 100, the rotors 102, etc. The increase in drag,coupled with a decrease in lift by the functional rotors, may allow thedrone 100 to land in a horizontal attitude. Stated another way, when oneor more rotors 102 of the drone 100 fail, drag created by the cages 110may allow the drone 100 to descend in a controlled manner using thefunctioning rotors 102.

For example, as disclosed herein, the drone 100 may include one or moreaccelerometers that can detect when the drone 100 tilts more than apreset amount of tilt. For instance, when a rotor fails, the drone 100may tilt more than 15° and the accelerometers may detect this tilt. Thetilt may signify a failed rotor or other malfunction. Once the failedrotor is detected, the power to any remaining functioning rotors may becut so that the aerodynamic effects of the cages 110 may cause the drone100 to descend in a horizontal configuration.

The size and shape of the ribs 206 and the spares 208 may be such thatthe ribs 206 and the spars 208 have a predetermined drag coefficient.For example, the height of the spars 208 and the height of the ribs 206may be twice the thickness of the ribs 206 and the spars 208. Thedifference in the dimensions may result in the ribs 206 and the spars208 having a drag coefficient ranging from about 0.7 to about 1.2.

In addition to the height being greater than the thickness, the ribs 206and the spars 208 may be shaped as airfoils. For example, as shown inFIG. 5 , the ribs 206 may be shaped such that an upper surface 502 ofthe rib 206 may generate lift as airflow 504 contacts a leading edge 506of the rib 206 and flows towards to trailing edge 508. The leading edge506 and the trailing edge 508 may define a cord line, which may be usedto define an angle of attack for the ribs 206 and the spars 208.

Turning now to FIG. 6 , FIG. 6 shows an example schematic of a drone 600(such as the drone 100 in FIGS. 1A and 1B) in accordance with someembodiments. As shown in FIG. 6 , the drone 600 may include the airframe602, a flight mechanism 604 (such as the rotors 102), and computingenvironment 606. The airframe 602 may be made of made of polymers,metals, etc. and the other components of the drone 600 may be secured tothe airframe 104.

The flight mechanism 604 may include mechanisms that may propel thedrone 600 through the air. For example, the flight mechanism 604 mayinclude rotors, turbofans, turboprops, etc. The flight mechanism 604 mayoperably interface with avionics 608. The avionics 608 may be part ofthe computing environment 606 (as shown in FIG. 6 ) or standalonecomponents. For example, the avionics 608 may include accelerometers610, an altimeter 612, gyroscopes 614, and a GPS receiver 616.

The various components of the avionics 608 may be standalone componentsor may be part of an autopilot system or other avionics package. Forexample, the altimeter 612 and GPS receiver 616 may be part of anautopilot system that includes one or more axes of control. Forinstance, the autopilot system may be a two-axis autopilot that maymaintain a preset course and hold a preset altitude. The avionics 608may be used to control in-flight orientation of the drone 600. Forexample, the avionics 608 may be used to control orientation of thedrone 600 about pitch, bank, and yaw axes while in flight. In addition,the avionics 608 may assist in landing the drone 600 in a controlledmatter should a rotor failure occur.

The avionics 608 may allow for autonomous flight. For example, asdescribed herein, the drone 600 may receive a flightpath that the drone600 may fly without further user input. In addition, the avionics 608may include a navigation transmitter 630 that may be used to transmitcommands to the flight mechanism 604. While FIG. 6 shows the navigationtransmitter 630 as part of the avionics 608, the navigation transmitter630 may be software stored in a memory 618 as shown by dashed navigationtransmitter 630.

The computing environment 606 may also include the memory 618 that maystore applications 620 and a drone operating system (OS) 622. Theapplications 620 may include a communications program that may allowdrone 600 to communicate with remote controls, other drones, andcomputing devices. In addition, the applications 620 may includesoftware that functions as the navigation transmitter 630.

The computing environment 606 may include a central processing unit(CPU) 624, a battery 626, and a communications interface 628. The CPU624 may be used to execute operations and method steps, such as thosedescribed herein with regard to FIG. 7 . The memory 618 also may storedata received by the drone 600 as well as programs and other softwareutilized by the drone 600. For example, the memory 618 may storeinstructions that, when executed by the CPU 624, cause the CPU 642 toperform operations such as those described herein.

The communications interface 628 may include transmitters, receivers, ortransceivers that may be used to communicate with a computing device.For example, the communications interface 628 may include an automaticdependent surveillance-broadcast (ADS-B) receiver (ADS-B In) ortransmitter (ADS-B Out) that may send and receive data. In addition, thecommunications interface 628 may include a cellular interface or otherwireless credential exchange modules. For example, the communicationsinterface 628 may include an ADS-B In-and-Out module that allows thedrone 600 to transmit its position and any error messages or otherflight status to a user.

While FIG. 6 shows various components of the drone 600, not allcomponents shown in FIG. 6 are required. For example, drone 600 may nothave the gyroscopes 614, the altimeter 614, etc.

FIG. 7 illustrates an example method 700 in accordance with someembodiments disclosed herein. The method 700 may begin at stage 702where a drone may detect a rotor failure. The rotor failure may bedetected via a variety of manners. For example, the applications 620 maydetect a voltage or current drop or spike for any one of the rotors 102.In addition, the drone 600 may utilize the gyroscopes 614 oraccelerometers 610 to detect an unusual attitude or other condition thatresults in a bank angle of the drone 600 exceeding a preset value.

Once the rotor failure is detected, the method 700 may proceed to stage704 where the drone may initiate a controlled descent. For example, upondetecting one or more rotor failures, the drone 600, via drone OS 622 orapplications 620, may decrease or increase power to functioning rotors.For instance, if two adjacent rotors failed (e.g., rotors 102C and102D), the drone 600 may detect an unusual attitude using the gyroscopes614. As a result, the drone OS 622 or the applications 620 may decreasepower to functioning rotors (e.g., rotors 102A and 102B). The power tothe functioning rotors may be decreased so as to cause the drone 600 todescend in a level flight attitude or substantially level flightattitude. A substantially level flight attitude may be a flight attitudewhere the drone 600 may not be in a level flight attitude, but thehorizontal movement of the drone 600 caused by the functioning rotors isminimal or within a preset distance. For example, a substantially levelflight attitude may include the drone 600 banked at 5 degrees with alateral displacement of less than 5 feet per 50 feet of altitude lost.The altitude lost and lateral displacement may be measured using the GPS616 and the altimeter 612.

In addition to decreasing power to the functioning rotors, the drone OS622 or applications 620 may completely deactivate the functioningrotors. For example, upon detecting a rotor failure, the drone OS 622 orapplications 620 may deactivate the functioning rotors such that no liftis being generated by the rotors. The lack of lift may cause the causethe drone 600 to descend. As the drone 600 descends, the aerodynamiceffects of the ribs 206 and the spars 208 may cause the drone 600 todescend in a controlled manner.

EXAMPLES

Example 1 is a drone rotor cage comprising: a motor housing; a pluralityof ribs extending from the motor housing, each of the plurality of ribshaving a rib height and a rib thickness, the rib height being greaterthan the rib thickness; and a plurality of spars, each of the sparsextending from a respective one of the plurality of ribs, each of theplurality of spars having a spar height and a spar thickness, the sparheight being greater than the spar thickness, wherein the plurality ofribs and the plurality of spars define a space sized to allow a rotor tospin freely when the rotor cage is attached to a drone.

In Example 2, the subject matter of Example 1 optionally includeswherein the rib height is greater than the rib thickness.

In Example 3, the subject matter of any one or more of Examples 1-2optionally include wherein the rib height is greater than the ribthickness.

In Example 4, the subject matter of any one or more of Examples 1-3optionally include wherein the spar thickness and the rib thickness areequal.

In Example 5, the subject matter of any one or more of Examples 1-4optionally include wherein the spar height and the rib height are equal.

In Example 6, the subject matter of any one or more of Examples 1-5optionally include wherein the rib height is twice the rib thickness.

In Example 7, the subject matter of any one or more of Examples 1-6optionally include wherein the spar height is twice the spar thickness.

In Example 8, the subject matter of any one or more of Examples 1-7optionally include wherein the plurality of spars and the plurality ofribs each includes a leading edge and a trailing edge.

In Example 9, the subject matter of any one or more of Examples 1-8optionally include wherein each of the plurality of spars have anairfoil shape.

In Example 10, the subject matter of any one or more of Examples 1-9optionally include wherein each of the plurality of ribs have an airfoilshape.

In Example 11, the subject matter of any one or more of Examples 1-10optionally include.

Example 12 is a drone comprising: a plurality of rotors attached to anairframe; and a rotor cage surrounding at least one of the plurality ofrotors, the rotor cage having a plurality of spars and a plurality ofribs configured to increase drag as the drone descends when at least oneof the plurality of rotors fails in flight.

In Example 13, the subject matter of Example 12 optionally includes amotor housing, the motor housing connected to the airframe proximate therotor, wherein the plurality of ribs extend from the motor housing andeach of the plurality of spars extend from a respective one of theplurality of ribs.

In Example 14, the subject matter of any one or more of Examples 12-13optionally include wherein each of the plurality of ribs has a ribheight and a rib thickness, the rib height being greater than the ribthickness.

In Example 15, the subject matter of any one or more of Examples 12-14optionally include wherein each of the plurality of spars has a sparheight and a spar thickness, the spar height being greater than the sparthickness.

In Example 16, the subject matter of Example 15 optionally includeswherein the rib height is greater than the rib thickness.

In Example 17, the subject matter of any one or more of Examples 15-16optionally include wherein the spar height is greater than the sparthickness.

In Example 18, the subject matter of any one or more of Examples 12-17optionally include wherein each of the plurality of spars and each ofthe plurality of ribs each includes a leading edge and a trailing edge.

In Example 19, the subject matter of any one or more of Examples 12-18optionally include wherein each of the plurality of spars have anairfoil shape.

In Example 20, the subject matter of any one or more of Examples 12-19optionally include wherein each of the plurality of ribs have an airfoilshape.

In Example 21, the subject matter of any one or more of Examples 12-20optionally include.

In Example 22, the subject matter of any one or more of Examples 12-21optionally include a processor; and a memory storing instructions that,when executed by the processor, cause the processor to: detect the rotorfailure, and initiate a controlled descent of the drone in response todetecting the rotor failure.

In Example 23, the subject matter of Example 22 optionally includeswherein initiating the controlled descent includes instructions that,when executed by the processor, cause the processor to deactivate theplurality of rotors.

In Example 24, the subject matter of any one or more of Examples 22-23optionally include wherein initiating the controlled descent includesinstructions that, when executed by the processor, cause the processorto adjust a power to at least one of the plurality of rotors to causethe drone to descend in a controlled flight attitude.

In Example 25, the subject matter of any one or more of Examples 22-24optionally include wherein detecting the rotor failure includesinstructions that, when executed by the processor, cause the processorto detect an unusual flight attitude.

In Example 26, the subject matter of any one or more of Examples 12-25optionally include wherein the rotor cage is one of a plurality of rotorcages.

Example 27 is a method of controlling a drone having an onboard computeroperatively connected to a plurality of rotors, the method comprising:detecting, by the onboard computer, a rotor failure; and initiating, bythe onboard computer, a controlled descent of the drone in response todetecting the rotor failure.

In Example 28, the subject matter of Example 27 optionally includeswherein initiating the controlled descent includes deactivating theplurality of rotors.

In Example 29, the subject matter of any one or more of Examples 27-28optionally include wherein initiating the controlled descent includesadjusting a power to at least one of the plurality of rotors to causethe drone to descend in a controlled flight attitude.

In Example 30, the subject matter of any one or more of Examples 27-29optionally include wherein detecting the rotor failure includesdetecting an unusual flight attitude.

In Example 31, the subject matter of Example 30 optionally includeswherein detecting the unusual flight attitude includes detecting a tiltangle greater than a preset tilt.

In Example 32, the subject matter of any one or more of Examples 27-31optionally include wherein detecting the rotor failure includesdetecting a voltage drop across one of the plurality of rotors.

In Example 33, the subject matter of any one or more of Examples 27-32optionally include wherein detecting the rotor failure includesdetecting a voltage spike across one of the plurality or rotors.

In Example 34, the subject matter of any one or more of Examples 27-33optionally include wherein detecting the rotor failure includesdetecting a current drop across one of the plurality of rotors.

In Example 35, the subject matter of any one or more of Examples 27-34optionally include wherein detecting the rotor failure includesdetecting a current spike across one of the plurality or rotors.

Example 36 is at least one computer-readable medium comprisinginstructions to perform any of the methods of Examples 27-35.

Example 37 is an apparatus comprising means for performing any of themethods of Examples 27-35.

Example 38 is a drone comprising: a plurality of rotors; means fordetecting a rotor failure; and means for initiating a controlled descentof the drone in response to detecting the rotor failure.

In Example 39, the subject matter of Example 38 optionally includeswherein the means for initiating the controlled descent includes meansfor deactivating the plurality of rotors.

In Example 40, the subject matter of any one or more of Examples 38-39optionally include wherein the means for initiating the controlleddescent includes means for adjusting a power to at least one of theplurality of rotors to cause the drone to descend in a controlled flightattitude.

In Example 41, the subject matter of any one or more of Examples 38-40optionally include wherein the means for detecting the rotor failureincludes means for detecting an unusual flight attitude.

In Example 42, the subject matter of Example 41 optionally includeswherein the means for detecting the unusual flight attitude includesmeans for detecting a tilt angle greater than a preset tilt.

In Example 43, the subject matter of any one or more of Examples 38-42optionally include wherein the means for detecting the rotor failureincludes means for detecting a voltage drop across one of the pluralityof rotors.

In Example 44, the subject matter of any one or more of Examples 38-43optionally include wherein the means for detecting the rotor failureincludes means for detecting a voltage spike across one of the pluralityor rotors.

In Example 45, the subject matter of any one or more of Examples 38-44optionally include wherein the means for detecting the rotor failureincludes means for detecting a current drop across one of the pluralityof rotors.

In Example 46, the subject matter of any one or more of Examples 38-45optionally include wherein the means for detecting the rotor failureincludes means for detecting a current spike across one of the pluralityor rotors.

Example 47 is at least one computer readable medium includinginstructions that, when executed by a processor, cause the processor to:detect a rotor failure; and initiate a controlled descent of the dronein response to detecting the rotor failure.

In Example 48, the subject matter of Example 47 optionally includeswherein initiating the controlled descent includes instructions that,when executed by the processor, cause the processor to deactivate theplurality of rotors.

In Example 49, the subject matter of any one or more of Examples 47-48optionally include wherein initiating the controlled descent includesinstructions that, when executed by the processor, cause the processorto adjust a power to at least one of the plurality of rotors to causethe drone to descend in a controlled flight attitude.

In Example 50, the subject matter of any one or more of Examples 47-49optionally include wherein detecting the rotor failure includesinstructions that, when executed by the processor, cause the processorto detect an unusual flight attitude.

In Example 51, the subject matter of Example 50 optionally includeswherein detecting the unusual flight attitude includes instructionsthat, when executed by the processor, cause the processor to detect atilt angle greater than a preset tilt.

In Example 52, the subject matter of any one or more of Examples 47-51optionally include wherein detecting the rotor failure includesinstructions that, when executed by the processor, cause the processorto detect a voltage drop across one of the plurality of rotors.

In Example 53, the subject matter of any one or more of Examples 47-52optionally include wherein detecting the rotor failure includesinstructions that, when executed by the processor, cause the processorto detect a voltage spike across one of the plurality or rotors.

In Example 54, the subject matter of any one or more of Examples 47-53optionally include wherein detecting the rotor failure includesinstructions that, when executed by the processor, cause the processorto detect a current drop across one of the plurality of rotors.

In Example 55, the subject matter of any one or more of Examples 47-54optionally include wherein detecting the rotor failure includesinstructions that, when executed by the processor, cause the processorto detect a current spike across one of the plurality or rotors.

Example 56 is at least one machine-readable medium includinginstructions that, when executed by processing circuitry, cause theprocessing circuitry to perform operations to implement of any ofExamples 1-55.

Example 57 is an apparatus comprising means to implement of any ofExamples 1-55.

Example 58 is a system to implement of any of Examples 1-55.

Example 59 is a method to implement of any of Examples 1-55.

The above detailed description includes references to the accompanyingdrawings, which form a part of the detailed description. The drawingsshow, by way of illustration, specific embodiments that may bepracticed. These embodiments are also referred to herein as “examples.”Such examples may include elements in addition to those shown ordescribed. However, also contemplated are examples that include theelements shown or described. Moreover, also contemplate are examplesusing any combination or permutation of those elements shown ordescribed (or one or more aspects thereof), either with respect to aparticular example (or one or more aspects thereof), or with respect toother examples (or one or more aspects thereof) shown or describedherein.

Publications, patents, and patent documents referred to in this documentare incorporated by reference herein in their entirety, as thoughindividually incorporated by reference. In the event of inconsistentusages between this document and those documents so incorporated byreference, the usage in the incorporated reference(s) are supplementaryto that of this document; for irreconcilable inconsistencies, the usagein this document controls.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In the appended claims, the terms “including” and“in which” are used as the plain-English equivalents of the respectiveterms “comprising” and “wherein.” Also, in the following claims, theterms “including” and “comprising” are open-ended, that is, a system,device, article, or process that includes elements in addition to thoselisted after such a term in a claim are still deemed to fall within thescope of that claim. Moreover, in the following claims, the terms“first,” “second,” and “third,” etc. are used merely as labels, and arenot intended to suggest a numerical order for their objects.

The above description is intended to be illustrative, and notrestrictive. For example, the above-described examples (or one or moreaspects thereof) may be used in combination with others. Otherembodiments may be used, such as by one of ordinary skill in the artupon reviewing the above description. The Abstract is to allow thereader to quickly ascertain the nature of the technical disclosure andis submitted with the understanding that it will not be used tointerpret or limit the scope or meaning of the claims. Also, in theabove Detailed Description, various features may be grouped together tostreamline the disclosure. However, the claims may not set forthfeatures disclosed herein because embodiments may include a subset ofsaid features. Further, embodiments may include fewer features thanthose disclosed in a particular example. Thus, the following claims arehereby incorporated into the Detailed Description, with a claim standingon its own as a separate embodiment. The scope of the embodimentsdisclosed herein is to be determined with reference to the appendedclaims, along with the full scope of equivalents to which such claimsare entitled.

The invention claimed is:
 1. A drone propeller cage comprising: a motorhousing to provide an opening for a rotor of a drone; a rotor armconnector to detachably couple to an arm that supports the rotor of thedrone; a plurality of ribs extending from the motor housing, theplurality of ribs including at least a first rib and a second rib; and aplurality of spars including at least a first spar and a second spar,the first spar located above the rotor arm connector, each of theplurality of ribs coupled to at least one of the plurality of spars, andeach of the first and second spars having a spar height and a sparthickness, the spar height being greater than the spar thickness, witheach of the first and second spars arranged in a partially or fullycircular shape that extends around the motor housing with a continuousspar height and spar thickness; the plurality of ribs and the pluralityof spars arranged to define a space that is sized to allow a propellercoupled to the rotor of the drone to spin freely when the propeller cageis mounted to the drone.
 2. The drone propeller cage of claim 1, each ofthe first and second ribs having a rib height and a rib thickness,wherein the rib height is greater than the rib thickness.
 3. The dronepropeller cage of claim 1, wherein the spar height and a rib thicknessof at least one respective spar and rib are equal.
 4. The dronepropeller cage of claim 1, wherein the spar height is at least twice thespar thickness.
 5. The drone propeller cage of claim 1, the plurality ofspars further including a third spar positioned between the first sparand the second spar.
 6. A drone, comprising: a plurality of rotorsattached to an airframe; and at least one propeller cage removablycoupled to the airframe, the at least one propeller cage adapted tosurround a respective rotor of the plurality of rotors, the propellercage comprising: a motor housing to provide an opening for therespective rotor; a rotor arm connector to detachably couple to an armthat supports the respective rotor; a plurality of ribs extending fromthe motor housing, the plurality of ribs including at least a first riband a second rib; and a plurality of spars including at least a firstspar and a second spar, the first spar located above the rotor armconnector, each of the plurality of ribs coupled to at least one of theplurality of spars, and each of the first and second spars having a sparheight and a spar thickness, the spar height being greater than the sparthickness, with each of the first and second spars arranged in apartially or fully circular shape that extends around the motor housingwith a continuous spar height and spar thickness; the plurality of ribsand the plurality of spars arranged to define a space that is sized toallow a propeller coupled to the respective rotor to spin freely whenthe propeller cage is coupled to the airframe.
 7. The drone of claim 6,each of the first and second ribs having a rib height and a ribthickness, wherein the rib height is greater than the rib thickness. 8.The drone of claim 6, wherein the spar height and a rib thickness of atleast one respective spar and rib are equal.
 9. The drone of claim 6,wherein the spar height is at least twice the spar thickness.
 10. Thedrone of claim 6, the plurality of spars further including a third sparpositioned between the first spar and the second spar.
 11. A cageassembly for a drone, comprising: a first drone propeller cage to attachto a first rotor of the drone; and a second drone propeller cage toattach to a second rotor of the drone, the first drone propeller cagecoupled to the second drone propeller cage; each of the first dronepropeller cage and the second drone propeller cage comprising: a motorhousing to provide an opening for a respective rotor; a rotor armconnector to detachably couple to an arm that supports the respectiverotor; a plurality of ribs extending from the motor housing, theplurality of ribs including at least a first rib and a second rib; and aplurality of spars including at least a first spar and a second spar,the first spar located above the rotor arm connector, each of theplurality of ribs coupled to at least one of the plurality of spars, andeach of the first and second spars having a spar height and a sparthickness, the spar height being greater than the spar thickness, witheach of the first and second spars arranged in a partially or fullycircular shape that extends around the motor housing with a continuousspar height and spar thickness; the plurality of ribs and the pluralityof spars arranged to define a space that is sized to allow a propellercoupled to the respective rotor to spin freely when the cage assembly ismounted to the drone.